John Killen/The OregonianThousands wait in Pioneer Courthouse Square on the chance that comedian Dave Chappelle might arrive for a free show. This photo was taken about 11:15 p.m., as the crowd was still building.

3 a.m.: According to numerous reports, comic Dave Chappelle arrived at Pioneer Courthouse Square about 1 a.m. to entertain those still on hand.

Thousands of people had packed the square late Tuesday and early Wednesday, hoping to catch site of Chappelle at was thought to be a midnight show.

As late as 12:30, there was still no sign of the comedian and actor, and some who had hoped to see Chappelle had begun leaving the square.

But some observers later reported seeing Chappelle arrive around 12:55 a.m. According to some bloggers and e-mailers who sent messages to The Oregonian, he didn't seem to have a suitable sound system, but was trying to find equipment to put on a show.

And at least one said the show he did present was worth the wait.

---1:30 a.m.: Thousands of people packed Pioneer Courthouse square late Tuesday and early Wednesday, hoping to catch site of comedian Dave Chappelle.

But as of 12:30 a.m., (Editor's note: An earlier version of this story erroneously said Chappelle had not appeared by 1:30 a.m.) there didn't seem to have been any sign of the popular actor and comic.

"Seem" is the operative word because the crowd was so dense and loud that Chappelle could have been standing in the center of the square and few would have known it.

The massive turnout was prompted by messages that went out on the Internet, many on Twitter, saying that Chappelle had decided to do an impromptu show at midnight. But the hour came and went without him appearing.

Still, the event clearly illustrated the ability of the Internet to summon thousands of people to one place, even if only on the chance of seeing, or taking part, in some sort of special event.

Even when the event isn't as advertised.

While no official estimate of the crowd was available, it was shoulder to shoulder in most places. Drawing on estimates done by The Oregonian during timber-related protests almost 20 years ago, such a gathering at the square could have reached close to 10,000 people.

John Killen/The OregonianThe crowd at Pioneer Courthouse Square was backed up to the edge of Sixth Avenue, and in some places spilled into the streets.

At least twice around 12:20, loud shouts and cheers began boiling up from the throng, seeming to signify that Chappelle had made an entrance. But neither time was there any sign of the man who became well known as the star of the "Chapelle Show," a sketch comedy heavy on social and cultural satire.

Chappelle's Web site made no mention of any appearance in Portland, but one man on the edge of crowd claimed to know that Chappelle had requested sound equipment for the show and that he had helped obtain it. But he didn't seem to have any further knowledge - except to say that Chappelle was staying at the nearby Heathman Hotel.

Police presence was heavy. Patrol cars and police motorcycles surrounded the square, often called Portland's living room.

However on this warm evening it looked, sounded -- and smelled --like Portland's favorite bar - a bar in the days before smoking was banned.

One officer who chased some of the crowd off one of the structures at the southwest corner of the square said he didn't know much, either - only that rumors of Chappelle's appearance had led to the call-out. But he, and other police, seemed to be enjoying the spectacle, if in a reserved fashion.

While the crowd was boisterous, and prone to climb anything that might lend a better view, there was no sign of any serious problems through 12:30.

By then, some people were beginning to leave the square, talking about the fact that the whole thing was taking on the feel a hoax.

Many others, however, did not seem upset; instead, they seemed to be enjoying the fact that they were part of a huge, impromptu "flash mob" - the sort of event that can happen in the age of instant messaging, Twitter and other social networking sites.

As of 1:30 a.m., the KGW video camera that looks down on the square showed that the crowd had diminished some, and Twitter feeds indicated that Chappelle had still not arrived.

But a short time later, other feeds began to appear, indicating the Chappelle had arrived.